1. Field of the Invention
The present invention relates to a hydraulic damper for a vehicle such as a motor vehicle which has a function of controlling (or adjusting) a height of the vehicle as well as its rolling rigidity (i.e., the rigidity with which the vehicle is rolled about a longitudinal axis of the vehicle).
2. Description of the Related Art
As a hydraulic damper for a vehicle, there has hitherto been known a twin-tube type and a mono-tube type. The twin-tube type of hydraulic damper is provided with an outer tube, an inner tube, and a rod provided at its lower end with a damper piston which is equipped with a valve mechanism. An oil chamber for inserting thereinto the damper piston is provided inside the inner tube. A reserve chamber which is in fluid flow communication with the oil chamber is provided between the outer tube and the inner tube.
The mono-tube type of hydraulic damper is provided with a cylindrical damper main body and a rod having mounted on a lower end thereof a damper piston which is equipped with a valve mechanism. An oil chamber into which the damper piston is inserted is provided inside the damper main body.
In order to improve the moving performance at the time of high-speed running, it becomes necessary to lower the vehicle height and to increase the rolling rigidity. Here, if the hydraulic damper is forcibly pushed and contracted, it becomes possible to lower the vehicle height and also to increase the rolling rigidity by regulating the lifting of the vehicle body on the side of the inner wheel at the time of cornering.
In view of the above-described points, the present invention has an object of providing such a hydraulic damper for a vehicle as will be able to be forcibly pushed and contracted by a hydraulic pressure from an outside pressure source.